This invention relates to an electromagnetic shutter controlling device for a camera. In particular, this invention relates to a shutter for a camera wherein an electromagnetic device including an armature and connected to an electrical delay circuit is provided for driving the system, the armature first charges the shutter and then releases the shutter successively to initiate an exposure while it is attracted by the electromagnet of the electromagnetic device. The exposure is maintained while the electromagnetic device is energized and the electromagnetic device is deenergized after a predetermined period of exposure time controlled by the delay circuit to complete the exposure by releasing the armature.
In the conventional shutter controlling device for a camera for controlling the exposure and having an electromagnetic device including an armature and connected to an electrical delay circuit, the shutter blade is directly engaged with the armature, when the electromagnetic device is energized by shutter releasing operation, the armature is attracted driving the shutter blade to open the shutter aperture while simultaneously straining a driving spring so that the driving spring will drive the shutter blade to close the shutter aperture when it is released, and the armature returns to the original position when the electromagnetic device is deenergized. This shutter of the conventional type has the following disadvantages, in the first place, that the movement of the armature is affected by frictional resistance and inertia of the shutter blade so that the time during which the armature moves a fixed distance becomes irregular, therefore, the time from the energizing of the electromagnetic device to the starting of the shutter blade and the time from the starting to the full open state of the shutter blade also become irregular so that the exposure time fluctuates at every exposure operation, and in the second place, that as the voltage of the battery for energizing the electromagnetic device drops, the electromagnetic force to attract the armature also drops so that foregoing the afore-mentioned fluctuation of the exposure time is amplified and at the same time, starting and full opening of the shutter blade is delayed due to slow movement of the armature resulting in under exposure.
These disadvantages are serious in photographing under natural lighting conditions where high shutter speed is used. The electromagnetic device of the shutter of this conventional type requires more than several hundred milli-amperes of electric current. The constant voltage device required for securing the aforesaid electric current is expensive and large sized. In case of such a large sized camera as a studio camera, the disadvantages of the conventional shutter may be overcome by the provision of a constant voltage device, however, in case of a small sized camera such as a portable camera, where the space for fitting the battery and the electromagnetic device is limited, no means has been developed to overcome those disadvantages.